| In the past decades,the global electronic communication industry has been developing rapidly.Under the background of widespread commercial use of the fourth-generation communication system,the world is actively promoting the development of the fifthgeneration communication system.As a key link in wireless communication,antenna is responsible for transmitting and receiving electromagnetic waves.In order to meet people's demand for higher information transmission speed,mobile terminal devices need to support wider frequency band and MIMO system.As the most representative device among mobile terminals,smart phone has been widely and deeply integrated into people's life,and its antenna design has been paid considerable attention by many researchers.In recent years,due to the development of smart phones towards multi-mode,the available space for designers is reduced and more antennas are required to be accommodated.Therefore,it is increasingly difficult to design mobile phone antennas.In this context,it is of great significance to study the mobile phone antenna with small clearance to meet the requirements of multi-band.In this paper,firstly,the research background and significance of mobile phone antenna in mobile terminals are described,and the current research status of mobile phone antenna is summarized.Then it introduces the common forms of antenna in mobile phone,several technical methods supporting multi-band design,and the difficulties and benefits of supporting multiple-input multiple-output(MIMO)system.Finally,based on the summary of the above methods and a large number of experiments,three mobile phone antenna designs with small clearance supporting multi-frequency band are proposed.In the third chapter of this paper,an eight-band coupling ring-antenna with small clearance is proposed.The design uses a L-shape branch for coupling feeding,and applies a lumped component matching circuit to adjust the impedance matching and expand bandwidth.The antenna structure is curved to achieve the goal of minification,and the broadband coverage of 698-960 MHZ and 1710-2690 MHZ is finally achieved.The antenna profile height is only 5mm and the floor clearance is 8mm.It has the advantages of simple structure and small space,and meets the multi-frequency communication requirements of plastic shell mobile phone.In the fourth chapter of this paper,a seven-band metal frame mobile phone antenna based on matching circuit is proposed.The multi-branch technique based on lumped element matching network is applied to make the radiation structures act in high and low frequency bands independent,which solves the problem of undesired mutual coupling between the high and low freqeuncy structures.Only a very limited space around the system circuit board is needed with a ground clearance of 1mm,and the antenna structure is very simple.The design idea and working mechanism of the matching circuit are described in detail.The design has been processed and measured.The results show that the propsoed antenna has great competitiveness for mobile phones in the era of full screen.In the fifth chapter,a 2×2 MIMO antenna for metal-framed mobile phones is presented.The antenna only occupies a minimum clearance of 1mm on the wide side of the circuit board of the system,which can support 7 bands,and does not use any narrow side space.The lowfrequency port uses the matching circuit to expand the bandwidth,while the high-frequency port uses the coupling feed technology to improve the matching.We provides a new solution for the multi-antenna layout of mobile phones in the 5G era. |
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